CN112794491A - Combined water treatment process for removing hexavalent chromium in wastewater - Google Patents
Combined water treatment process for removing hexavalent chromium in wastewater Download PDFInfo
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- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 60
- 239000002351 wastewater Substances 0.000 title claims abstract description 53
- 238000011282 treatment Methods 0.000 title claims abstract description 50
- 230000008569 process Effects 0.000 title claims abstract description 44
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 37
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000001301 oxygen Substances 0.000 claims abstract description 24
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 24
- 239000002253 acid Substances 0.000 claims abstract description 19
- 230000009467 reduction Effects 0.000 claims abstract description 18
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 6
- 239000011593 sulfur Substances 0.000 claims abstract description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 20
- 238000005273 aeration Methods 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 14
- HRZFUMHJMZEROT-UHFFFAOYSA-L sodium disulfite Chemical compound [Na+].[Na+].[O-]S(=O)S([O-])(=O)=O HRZFUMHJMZEROT-UHFFFAOYSA-L 0.000 claims description 11
- 229940001584 sodium metabisulfite Drugs 0.000 claims description 11
- 235000010262 sodium metabisulphite Nutrition 0.000 claims description 11
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- 239000007789 gas Substances 0.000 claims description 5
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 4
- DWAQJAXMDSEUJJ-UHFFFAOYSA-M Sodium bisulfite Chemical compound [Na+].OS([O-])=O DWAQJAXMDSEUJJ-UHFFFAOYSA-M 0.000 claims description 3
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 claims description 3
- 150000007513 acids Chemical class 0.000 claims description 2
- DJEHXEMURTVAOE-UHFFFAOYSA-M potassium bisulfite Chemical compound [K+].OS([O-])=O DJEHXEMURTVAOE-UHFFFAOYSA-M 0.000 claims description 2
- 229940099427 potassium bisulfite Drugs 0.000 claims description 2
- 235000010259 potassium hydrogen sulphite Nutrition 0.000 claims description 2
- RWPGFSMJFRPDDP-UHFFFAOYSA-L potassium metabisulfite Chemical compound [K+].[K+].[O-]S(=O)S([O-])(=O)=O RWPGFSMJFRPDDP-UHFFFAOYSA-L 0.000 claims description 2
- 229940043349 potassium metabisulfite Drugs 0.000 claims description 2
- 235000010263 potassium metabisulphite Nutrition 0.000 claims description 2
- BHZRJJOHZFYXTO-UHFFFAOYSA-L potassium sulfite Chemical compound [K+].[K+].[O-]S([O-])=O BHZRJJOHZFYXTO-UHFFFAOYSA-L 0.000 claims description 2
- 235000019252 potassium sulphite Nutrition 0.000 claims description 2
- 238000007789 sealing Methods 0.000 claims description 2
- 235000010265 sodium sulphite Nutrition 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 1
- 230000001502 supplementing effect Effects 0.000 claims 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 7
- 229910052804 chromium Inorganic materials 0.000 abstract description 7
- 239000011651 chromium Substances 0.000 abstract description 7
- 239000003814 drug Substances 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 239000003795 chemical substances by application Substances 0.000 abstract description 2
- 229940079593 drug Drugs 0.000 abstract description 2
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 230000001376 precipitating effect Effects 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 10
- 230000014759 maintenance of location Effects 0.000 description 7
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 5
- 238000006392 deoxygenation reaction Methods 0.000 description 5
- 229910001873 dinitrogen Inorganic materials 0.000 description 4
- 238000012163 sequencing technique Methods 0.000 description 4
- 125000004122 cyclic group Chemical group 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- -1 hydrogen ions Chemical class 0.000 description 3
- 239000010842 industrial wastewater Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 239000013589 supplement Substances 0.000 description 2
- 238000004065 wastewater treatment Methods 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 230000007935 neutral effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
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- 231100000331 toxic Toxicity 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
- C02F1/32—Treatment of water, waste water, or sewage by irradiation with ultraviolet light
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/70—Treatment of water, waste water, or sewage by reduction
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
Abstract
The invention provides a combined water treatment process for removing hexavalent chromium in wastewater, which comprises the following steps: s1, adding sufficient or excessive sulfur-based reducing agent into the wastewater; s2, deoxidizing the wastewater treated by the step S1; and S3, carrying out ultraviolet reinforced reduction on the wastewater after oxygen removal. The invention provides a novel combined process for treating hexavalent chromium wastewater, and three stages of processes are mutually cooperated, so that the hexavalent chromium is cleanly and efficiently removed. The method is simple, does not need expensive equipment and medicines, greatly reduces the dosage of reducing agent and acid, greatly saves the use of agents for precipitating trivalent chromium at the later stage, obviously reduces the overall treatment cost and is more beneficial to environmental protection.
Description
Technical Field
The invention relates to the technical field of industrial wastewater treatment, in particular to a treatment method of hexavalent chromium in wastewater.
Background
Hexavalent chromium is a highly toxic heavy metal pollutant and is widely present in industrial wastewater such as electroplating wastewater, tanning wastewater and the like. Reducing hexavalent chromium into trivalent chromium by adding a reducing agent and then removing the trivalent chromium by precipitation is the main method for treating hexavalent chromium wastewater at present. The most widely used and cost-effective reducing agents are the sulfur-based reducing agents including sodium bisulfite, sodium metabisulfite, and the like. However, the hexavalent chromium reduction process consumes a large amount of hydrogen ions, and these reducing agents all show a fast removal rate and a good removal rate only under acidic conditions. This requires the additional addition of acid as a source of hydrogen ions during the process, which not only adds additional cost to the reagent, but also adds to the cost of removing trivalent chromium by subsequent precipitation. More seriously, the removing effect of the reducing agent on the low-concentration hexavalent chromium is greatly reduced along with the consumption of hydrogen ions in the reaction. In order to further treat the low-concentration hexavalent chromium to reach the standard, reducing agents and acids which are several times of the stoichiometric amount are usually required to be added, so that the treatment cost is greatly increased. Therefore, the cost of the medicament is the main cost in the hexavalent chromium removal technology, and the effect that the concentration of the hexavalent chromium can reach the standard by realizing low dosage through developing a new treatment technology has important significance.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a combined water treatment process for removing hexavalent chromium in wastewater, which solves the problems that the dosage of a reducing agent and acid in the prior art is required to be several times of the theoretical dosage, and the subsequent precipitation process of trivalent chromium is influenced.
According to the embodiment of the invention, the combined water treatment process for removing hexavalent chromium in wastewater comprises the following steps:
s1, adding sufficient or excessive sulfur-based reducing agent into the wastewater;
s2, deoxidizing the wastewater treated by the step S1;
and S3, carrying out ultraviolet reinforced reduction on the wastewater after oxygen removal.
Preferably, the sulfur-based reducing agent described in steps S1 and S3 is one or more of sodium bisulfite, potassium bisulfite, sodium sulfite, potassium sulfite, sodium metabisulfite, and potassium metabisulfite.
To ensure sufficient reaction, the wastewater may be left to stand for 30 seconds after S1 before being introduced into the next process, and if in the continuous inlet/outlet mode, the hydraulic retention time is at least 30 seconds.
Preferably, the deoxygenation method in step S2 selects nitrogen gas to perform cyclic aeration deoxygenation, that is, a cyclic aeration pump is arranged in the sealed deoxygenation tank to pump the gas at the top of the deoxygenation tank to the bottom of the deoxygenation tank for cyclic aeration. When the concentration of dissolved oxygen in the effluent of the oxygen removal tank is higher than 1mg/L, the top gas is evacuated and new nitrogen is added. The aeration rate is 0.01-100L/min, and the hydraulic retention time is not less than 30 s.
Preferably, the wavelength of the ultraviolet light source used for the ultraviolet-enhanced reduction in step S3 is in a main range of 180 to 400 nm.
Preferably, the time for the ultraviolet-enhanced reduction in step S3 is not less than 0.5 h. The addition or non-addition of the reducing agent at the start of the step S3 is determined as needed and the amount of the reducing agent added in the step S1.
Preferably, the pH is adjusted to less than 8 in step S3 by adding an acid, which is one or more strong inorganic acids in combination. Such as one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Organic acid is not adopted to avoid adding extra COD, and strong acid is selected to improve the regulation efficiency, reduce the dosage and reduce the cost.
Preferably, the devices used in the steps S1-S3 are a reaction tank, an oxygen removal tank and a deep treatment tank respectively, the oxygen removal tank is provided with a sealing cover plate and a circulating aeration pump, the deep treatment tank is provided with a plurality of ultraviolet lamp tubes, and the arrangement distance of the ultraviolet lamp tubes is preferably 1-20 cm. The wastewater in the deoxidizing tank accounts for 70-90% of the total volume of the deoxidizing tank, the wastewater cannot enter a gas circuit when the gas circulation is avoided due to excessive addition of the wastewater, and the nitrogen supplement amount is large due to the fact that the nitrogen supplement amount is too small, so that the deoxidizing tank is not practical.
The water outlet mode of the advanced treatment tank is a sequencing batch mode or a continuous mode.
The technical principle of the invention is as follows: through research, the sulfite can be activated under neutral condition by ultraviolet illumination, reducing electrons with strong reducing capability are generated, and the reduction of hexavalent chromium is realized. However, experiments show that the method can only treat the hexavalent chromium wastewater with low concentration, and has little effect on the hexavalent chromium with high concentration in the actual industrial wastewater. In addition, studies have found that this method is not effective in oxygen-containing water bodies because oxygen reacts with the reducing electrons prior to hexavalent chromium. The above disadvantages result in a lack of practical value for the process.
The above-mentioned principle of this application make full use of research discovery has established neotype syllogic processing method, and the first section adds the medicine under keeping the higher effect cost ratio condition, reduces hexavalent chromium concentration to certain extent, and the second section adopts circulation nitrogen gas aeration method to reduce oxygen concentration, and the third section utilizes array ultraviolet fluorescent tube to carry out the irradiation activation to waste water, forms neotype hexavalent chromium waste water treatment combination technology. Compared with the traditional process, the novel process does not pursue the simple utilization of the reducing agent to realize the standard reaching of the concentration of the hexavalent chromium, thereby keeping higher utilization efficiency of the reducing agent.
It is worth to say that the basic concept of the invention is to construct a novel three-stage combined process: in the first stage, the concentration of hexavalent chromium in the wastewater is reduced to a lower level with high utilization efficiency of the reducing agent, and because complete standard-reaching removal in one step is not pursued, higher utilization rate of the reducing agent can be realized. In the second stage, the nitrogen gas circulating aeration method is adopted to remove the dissolved oxygen in the water body, and the complete removal of the dissolved oxygen is not required, so that the nitrogen gas circulating aeration method with low cost can meet the requirement. And in the third stage, a low-dose reducing agent and acid are added according to needs, and the ultraviolet irradiation enhancement effect is adopted to carry out advanced treatment on the water body with low hexavalent chromium concentration and low dissolved oxygen, so that the effluent reaches the standard. The three stages of reaction processes are combined with each other to form the hexavalent chromium combined water treatment process with low cost.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a novel combined process for treating hexavalent chromium wastewater, and three stages of processes are mutually cooperated, so that the hexavalent chromium is cleanly and efficiently removed. The method is simple, does not need expensive equipment and medicines, greatly reduces the dosage of reducing agent and acid, greatly saves the use of agents for precipitating trivalent chromium at the later stage, obviously reduces the overall treatment cost and is more beneficial to environmental protection.
Drawings
FIG. 1 is a graph comparing the hexavalent chromium concentrations after reduction in comparative examples 1-4.
FIG. 2 is a graph showing the hexavalent chromium concentration at each stage of comparative example 5.
FIG. 3 is a graph showing the hexavalent chromium concentration at each stage of comparative example 6.
FIG. 4 is a graph showing the concentration of hexavalent chromium at each stage of example 1
FIG. 5 is a graph showing the concentration of hexavalent chromium at each stage of example 2
FIG. 6 is a graph showing the concentration of hexavalent chromium at each stage of example 3
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. Various substitutions and alterations can be made without departing from the technical idea of the invention and the scope of the invention is covered by the present invention according to the common technical knowledge and the conventional means in the field.
Comparative examples 1 to 4: the method comprises the steps of setting a reaction tank by taking wastewater with the hexavalent chromium concentration of 50mg/L as a treatment object, introducing the wastewater into the reaction tank, adding sodium metabisulfite into the reaction tank by taking the sodium metabisulfite as a reducing agent, wherein the adding amount ratios of the reducing agent are respectively 250g/t, 500g/t, 750g/t and 1000g/t, standing for 1h for 15min and 30s, and then detecting the concentration of the residual hexavalent chromium in the water body by adopting an ultraviolet-visible spectrophotometry, wherein the concentration of the hexavalent chromium is shown in figure 1.
Comparative example 5: the method takes the wastewater with the hexavalent chromium concentration of 50mg/L as a treatment object and comprises the following steps:
1) set up the reaction tank, leading-in waste water in the reaction tank, add sodium metabisulfite and be the reductant, the reductant is thrown the volume and is compared: 250 g/t.
2) And (3) after adding the reducing agent, standing for 15min and 30s, and introducing the wastewater into a closed advanced treatment tank containing array ultraviolet lamp tubes, wherein the arrangement distance of the ultraviolet lamp tubes is 4 cm. Adding low-dose sodium metabisulfite with the adding amount of 1 g/t. Adding low-dose acid, adopting 98% concentrated sulfuric acid, and adjusting the pH value to 4. The operation is carried out in a sequencing batch mode, and the hydraulic retention time is 1 h.
3) And discharging water to finish the treatment of the hexavalent chromium in the wastewater.
The effluent hexavalent chromium concentration of each treatment process stage was measured by uv-vis spectrophotometry to show the effectiveness of the combined process, and the results can be seen in fig. 2. Therefore, the method does not adopt an aeration oxygen removal step, the ultraviolet strengthening reduction effect is not good, and the final concentration of hexavalent chromium is 2.16mg/L which is obviously higher than 0.5mg/L required by national standard.
Comparative example 6: the method takes the wastewater with the hexavalent chromium concentration of 50mg/L as a treatment object and comprises the following steps:
1) set up the reaction tank, leading-in waste water in the reaction tank, add sodium metabisulfite and be the reductant, the reductant is thrown the volume and is compared: 250 g/t.
2) And (4) standing for 30s after the reducing agent is added, and guiding the wastewater into an oxygen removal tank.
3) 99.9 percent of nitrogen is continuously aerated in the sealed deoxidizing pool by a circulating aeration pump, the aeration rate is 2L/min, and the hydraulic retention time is 900 s.
4) And the water discharged from the deoxidizing pool is then led into a closed advanced treatment pool containing an array ultraviolet lamp tube, and the ultraviolet lamp tube is closed. Adding low-dose sodium metabisulfite with the adding amount of 1 g/t. Adding low-dose acid, adopting 98% concentrated sulfuric acid, and adjusting the pH value to 4. The operation is carried out in a sequencing batch mode, and the hydraulic retention time is 1 h.
5) And discharging water to finish the treatment of the hexavalent chromium in the wastewater.
The effluent hexavalent chromium concentration of each treatment process stage was measured by uv-vis spectrophotometry to show the effectiveness of the combined process, and the results can be seen in fig. 3. After the treatment of the combined process, the concentration of the hexavalent chromium in the effluent is reduced to 0.48mg/L, and the national discharge standard is met.
Example 1:
a three-stage treatment process capable of realizing low-cost standard-reaching removal of hexavalent chromium in wastewater takes wastewater with the concentration of the hexavalent chromium being 50mg/L as a treatment object, and comprises the following steps:
1) set up the reaction tank, leading-in waste water in the reaction tank, add sodium metabisulfite and be the reductant, the reductant is thrown the volume and is compared: 250 g/t.
2) And (4) standing for 30s after the reducing agent is added, and guiding the wastewater into an oxygen removal tank.
3) 99.9 percent of nitrogen is continuously aerated in the sealed deoxidizing pool by a circulating aeration pump, the aeration rate is 2L/min, and the hydraulic retention time is 900 s.
4) The water discharged from the deoxidizing pool is then led into a closed advanced treatment pool containing array ultraviolet lamp tubes, and the arrangement distance of the ultraviolet lamp tubes is 4 cm. Adding low-dose sodium metabisulfite with the adding amount of 1 g/t. Adding low-dose acid, adopting 98% concentrated sulfuric acid, and adjusting the pH value to 4. The operation is carried out in a sequencing batch mode, and the hydraulic retention time is 1 h.
5) And discharging water to finish the treatment of the hexavalent chromium in the wastewater.
The effluent hexavalent chromium concentration of each treatment process stage was measured by uv-vis spectrophotometry to show the effectiveness of the combined process, and the results can be seen in fig. 4. After the treatment of the combined process, the concentration of the hexavalent chromium in the effluent is reduced to 0.06mg/L, and the national discharge standard is met.
Example 2:
the other steps of this example are the same as example 1 except that the pH of the deep treatment tank is adjusted to 5 by adding acid. The effluent hexavalent chromium concentration of each treatment process stage was measured by uv-vis spectrophotometry to show the effectiveness of the combined process, and the results can be seen in fig. 6. After the treatment of the combined process, the concentration of the hexavalent chromium in the effluent is reduced to 0.29mg/L, and the national discharge standard is met.
Example 3:
the other steps of the embodiment are the same as the embodiment 1, except that no reducing agent and no acid are additionally added into the advanced treatment tank, and the pH value is measured to be 6.2. The effluent hexavalent chromium concentration of each treatment process stage was measured by uv-vis spectrophotometry to show the effectiveness of the combined process, and the results can be seen in fig. 5. After the treatment of the combined process, the concentration of the hexavalent chromium in the effluent is reduced to 0.36mg/L, and the national discharge standard is met.
The reduction parameters and results of comparative examples 1-6 and examples 1-3 are shown in Table 1.
TABLE 1 reduction parameters and results comparison Table
As can be seen from the table, the reduction effect of example 1 is the best. Comparative examples 1-4 did not remove oxygen, irradiate UV light and add acid, and it can be seen that this conventional process is intended to achieve the state specified Cr6+At the emission standard (0.5mg/L), at least three times the amount of the reducing agent of example 1 is required, and at least 4 times the amount of the reducing agent of example 1 is required to achieve the reduction effect of example 1. It can be seen that the three-stage combined water treatment process of the present application provides a significant savings in the amount of reducing agent used.
Comparative example 5 is a comparative example of example 1, which demonstrates that the desired reduction effect cannot be achieved by direct irradiation of ultraviolet light without oxygen removal, which is indispensable.
Compared with the example 1, the visible ultraviolet light has strong promotion effect on the reduction of low-concentration chromium, and the emission concentration of hexavalent chromium is reduced by one order of magnitude by irradiating the ultraviolet light under the same condition.
The comparison of examples 1-3 highlights mainly the effect of the amount of acid added on the reduction effect. It can be seen that the lower the pH, the better the reduction, but example 3, which does not additionally add acid to lower the pH, already reaches the national emission standards.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (10)
1. A combined water treatment process for removing hexavalent chromium in wastewater is characterized by comprising the following steps:
s1, adding sufficient or excessive sulfur-based reducing agent into the wastewater;
s2, deoxidizing the wastewater treated by the step S1;
and S3, carrying out ultraviolet reinforced reduction on the wastewater after oxygen removal.
2. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 1, wherein: the sulfur-based reducing agent is one or a mixture of sodium bisulfite, potassium bisulfite, sodium sulfite, potassium sulfite, sodium metabisulfite and potassium metabisulfite.
3. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 1, wherein: the oxygen removal method in the step S2 is to remove oxygen by nitrogen aeration and continue until the dissolved oxygen concentration is not higher than 1 mg/L.
4. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 3, wherein: the oxygen removal method in the step S2 is nitrogen circular aeration oxygen removal, and the purity of the used nitrogen is more than 90%.
5. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 4, wherein: and the aeration rate in the step S2 is 0.01-100L/min, and the oxygen removal time is not less than 30S.
6. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 1, wherein: the wavelength of the ultraviolet light source used for the ultraviolet-enhanced reduction in the S3 includes 180-400 nm.
7. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 6, wherein: the time of the ultraviolet-enhanced reduction in the step S3 is not less than 0.5 h.
8. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 1, wherein: and in the step S3, adding acid to adjust the pH to be less than 8, and supplementing a reducing agent, wherein the acid is one or more mixed inorganic strong acids.
9. The combined water treatment process for removing hexavalent chromium from wastewater according to any one of claims 1 to 8, wherein: the equipment used in the steps S1-S3 is respectively a reaction tank, a deoxidizing tank and a deep treatment tank, wherein the deoxidizing tank is provided with a sealing cover plate, and the deep treatment tank is provided with a plurality of ultraviolet lamp tubes.
10. The combined water treatment process for removing hexavalent chromium from wastewater according to claim 9, wherein: the gas at the top of the deoxidizing pool is recycled, and the waste water accounts for 70-90% of the volume of the deoxidizing pool.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20070187001A1 (en) * | 2006-02-14 | 2007-08-16 | Kirk Kramer | Composition and Processes of a Dry-In-Place Trivalent Chromium Corrosion-Resistant Coating for Use on Metal Surfaces |
| CN101264953A (en) * | 2008-04-18 | 2008-09-17 | 中国科学院化学研究所 | Photochemical reduction method for treating chromium-containing waste water without additional reducing agent and sacrificial agent |
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| CN105731587A (en) * | 2015-12-18 | 2016-07-06 | 南京大学 | Method for reducing hexavalent chromium through micromolecular diketone-ultraviolet light |
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| CN107601737A (en) * | 2017-11-15 | 2018-01-19 | 重庆大学 | A kind of method that matrix auxiliary UV photocatalysis removes mercury in organic sewage |
| US20190270657A1 (en) * | 2018-03-02 | 2019-09-05 | Earth Renaissance Technologies, Llc | Method for reducing selenium and heavy metals in industrial wastewaters |
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